Diffusion‐controlled vinyl polymerization. III. Free volume parameters and diffusion‐controlled propagation

Soh, S. K.; Sundberg, Donald C.

doi:10.1002/pol.1982.170200515

Cited by 96 publications

(45 citation statements)

References 23 publications

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“…Soh et al pointed out that the entanglement of a linear polymer chain, like polyisoprene, also occurred without cross linking as the polymer concentration and/or molecular weight increased. [26][27][28][29] They also explained the occurrence of an entanglement of a polymer chain whose molecular weight was more than ca. 10 4 , large enough to cause a transient network structure.…”

Section: Temperature Dependence Of T1 and T2mentioning

confidence: 98%

Pulsed NMR Study of the Curing Process of Epoxy Resin

et al. 2008

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Section: Temperature Dependence Of T1 and T2mentioning

confidence: 98%

Pulsed NMR Study of the Curing Process of Epoxy Resin

et al. 2008

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“…Soh et al pointed out that in a bulk polymerization of MMA, the entanglement of polymer chains occurred as the polymer concentration and/or molecular weight increased. [16][17][18][19] They also explained that the gel effect is closely related to a change of the free volume and the occurrence of the entanglement of a polymer chain whose molecular weight is more than ca. 10 4 .…”

Section: Reaction Time Dependence Of the Spin-spin Relaxation Timesmentioning

confidence: 99%

Pulsed NMR Study of Network Formation in the Course of Bulk Polymerization of Methyl Acrylate

et al. 2005

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Pulsed NMR can be used to elucidate certain aspects of the polymer structure and those properties that are affected by the molecular mobility. The spin-spin relaxation time (T2), which is primarily determined by the relatively slow motion of the polymer chain in the fluid state, was found to be useful for investigating the polymer structural order, chain entanglement and their presence as permanent cross-links. 1-3 Short polymer chains in a liquid state or at high temperature in the molten state will give rise to a single exponential T2 decay. When the molecular weight exceeds a critical value, the spin-spin relaxation deviates from the single exponential behavior. This is explained by the presence of higher molecular weights of molecular entanglements sufficient in number to provide a three dimensional network. 4 The entanglement of a polymer chain restricts the chain mobility. Since this long-range chain motion affects the NMR relaxation times, the studying T2 can provide a sensitive probe with which to investigate the effect of intermolecular coupling on the mobility.Most of molecular motion studies, however, have focused on polymers in a static state, such as cross-linked rubbers, 5 polymer melts with non-disperse molecular weight. 3 From a molecular motional point of view, bulk polymerization is also one of the most interesting targets for pulsed NMR spectroscopy. The reaction is followed by a liquid-to-solid transition accompanied by a change in the polymer structure, the molecular weight distribution and the density. The molecular motion during the course of the reaction is, therefore, continuously influenced particularly by the propagation process, where the entanglement occurs along with a rapid increase in the degree of polymerization. Under such circumstances, samples consist of a mixture of high-polymer, low-molecular weight polymer, oligomers, and a residual monomer where high molecular weight entangled (network structure) molecules co-exist with low molecular weight "free molecules". The constituents' fractions also continuously change during the reaction. In terms of the molecular motion, studying the network formation by a pulsed NMR method in a kinetic process, such as bulk polymerization, is therefore of interest and worth investigating as well as that by the gravimetric method, 6-9 because the pulsed NMR method provides such a different perspective on the kinetic process of the reaction in real time.In the present work, the proton spin-spin relaxation time of poly(methyl acrylate) (PMA) was measured in order to study network formation as a function of the reaction time at various temperatures by the pulsed NMR method. The results were considered in conjunction with that of 13 C DD/MAS NMR measurements and the polymer yield. ExperimentalPulsed NMR measurements were carried out with a JEOL Mu-25 spectrometer operating at a frequency of 25 MHz. The proton spin-spin relaxation time (T2) was obtained from the free induction decay (FID), which follows a 90˚ pulse. 10 The pulse interval time was 10 s...

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“…It should be mentioned that if a considerable number of trial runs were performed to determine suitable choices for the computational parameters (p c , p m , , and ␣ sh ), it would have been possible to eliminate the scatter in the optimal solutions obtained (Figs. [2][3][4][5]. However, this was not done because this would be computationally quite intensive, and the gains are minimal.…”

Section: Table VIII Decision Variables For a Few Chromosomes Of The Pmentioning

confidence: 99%

“…A t cross-sectional area of the PFTR (m 2 ) b 1 , b 2 , b 3 coefficients describing T w (z) (K/m, K/m 2 , K/m 3 ) C p,mix specific heat of the reaction mixture in the film reactor (J/ kg-K) D n dead polymer molecule having n repeat units E d , E p , E t activation energies for the reactions in Greek Letters ␣ sh exponent controlling the sharing effect in NSGA ␥ overlap factor maximum normalized distance in u space between any two chromosomes (solutions) ml defined in Table IV 13 , I3 ratio of the molar volume of the monomer and initiator jumping unit to the critical molar volume of the polymer, …”

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confidence: 99%

Multiobjective optimization of the continuous casting process for poly (methyl methacrylate) using adapted genetic algorithm

Zhou

Gupta

Ray

2000

J. Appl. Polym. Sci.

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The nondominated sorting genetic algorithm (NSGA) has been used to optimize the operation of the continuous casting of a film of poly (methyl methacrylate). This process involves two reactors, namely, an isothermal plug flow tubular reactor (PFTR) followed by a nonisothermal film reactor. Two objective functions have been used in this study: the cross‐section average value of the monomer conversion, x̄mf , of the product is maximized, and the length, zf , of the film reactor is minimized. Simultaneously, the cross‐section average value of the number‐average molecular weight of the product is forced to have a certain prescribed (desired) value. It is also ensured that the temperature at any location in the film being produced lies below a certain value, to avoid degradation reactions. Seven decision variables are used in this study: the temperature of the isothermal PFTR, the flow rate of the initiator in the feed to the PFTR (for a specified feed flow rate of the monomer), the film thickness, the monomer conversion at the output of the PFTR, and three coefficients describing the wall temperature to be used in the film reactor. Sets of nondominating (equally good) optimal solutions (Pareto sets) have been obtained due to the conflicting requirements for the several conditions studied. It is interesting to observe that under optimal conditions, the exothermicity of the reactions drives them to completion near the center of the film, while heat conduction and higher wall temperature help to achieve this in the outer regions. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1439–1458, 2000

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Diffusion‐controlled vinyl polymerization. III. Free volume parameters and diffusion‐controlled propagation

Cited by 96 publications

References 23 publications

Pulsed NMR Study of the Curing Process of Epoxy Resin

Pulsed NMR Study of the Curing Process of Epoxy Resin

Pulsed NMR Study of Network Formation in the Course of Bulk Polymerization of Methyl Acrylate

Multiobjective optimization of the continuous casting process for poly (methyl methacrylate) using adapted genetic algorithm

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